Dumb question about oil change/capacity

So I did the first oil change on my XJ the other day and was told to add 4.5 quarts and then fill accordingly and it seems like a lot of people get different variations. Anyway, I added probably 4.5-4.75 quarts of 10w-30 and while the engine was still relatively hot, it said full. I have driven it a few days including yesterday cruising around in the snow for awhile. I checked it today after it had been sitting for a few hours and its just about full. It is actually at the F on SAFE on the dipstick. My question is, should I add more just to be safe? Also, would I have done any damage by not adding enough? Thanks. -James

Oh and btw, my oil pressure has been normal/completely perfect. My temp has also been fine usually around 210. Yesterday, I did notice that the temp was sitting at the notch above 210 but I think this is because I was playing pretty hard in the snow.

just keep it at the full line and you're good to go. bottom to top of the safe marks on the dipstick is generally 1qt.

I've run 4.0s with as little as 1.5 quarts in them on level surfaces, anything below about 3 is risking running dry though. Happens to me once in a while when I forget to fill the MJ up (it's got a bad oil leak from the rear main seal.) If you corner hard, accelerate/brake hard, or wheel it, you will run dry with more than that in the sump, that's for sure.

Don't over-fill. While a half-quart won't do anything bad, it's not necessary. Just fill to anywhere in the Safe range. You won't hurt the engine running at the bottom of the range, or even a full quart low.

It should be 5 quarts if it's dry. The variation has to do with buildup in the pan, oil left in the oil galleys/passages, oil not finished draining back out of the head/cam galley, dents in the oil pan, etc.

Six qts. with a dry filter should put you in the "Safe " range on the dipstick.I usually pre-fill the filter with one of the 6 qts.

Alright thanks for the replies guys...today after it sits all day I"ll go out and check it and then add if necessary since it's all in the pan now. But I have a feeling max is going to be like 5 quarts I just don't see how it could take 6.

jamesonw23 said:

Alright thanks for the replies guys... I just don't see how it could take 6.

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If you have the I6 motor, it'll take 6qt - it was designed to take 6 whether you "see" it or not. I always put 6 full quarts in mine when I change the oil. And I'm anal ... I let it drain until there's zero drips, and when I pour the new oil in I wait until the bottle is darn near dry before moving on to the next.

Wayne Sihler said:

Six qts. with a dry filter should put you in the "Safe " range on the dipstick.I usually pre-fill the filter with one of the 6 qts.

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Same here and I always end up right at the full line.

Mighty.Mighty_XJ said:

If you have the I6 motor, it'll take 6qt - it was designed to take 6 whether you "see" it or not. I always put 6 full quarts in mine when I change the oil. And I'm anal ... I let it drain until there's zero drips, and when I pour the new oil in I wait until the bottle is darn near dry before moving on to the next.

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This.....X2...

Alright I'll take your advice and add until I'm full. Do you think I have done any harm? My oil pressure has been good and normal. But like I said, the other night I was out driving pretty hard in the snow and my temp was almost at the notch above 210. Highest I've seen it but I haven't had the Jeep that long so I'm just wondering.

I would be shocked if you did. As long as the oil pressure stays up and you're above a couple quarts you will be fine. If you ever hear valves clattering after the first few seconds from startup, shut it down and check your oil level.

Better a little low than overfull.

The amount of oil you will get into your 4.0 will also be influenced by the quality of the oil filter and the size of the oil filter.

Those really crappy oil filters with the nitrile rubber anti-drain back valves will allow oil out of the filter back into the crankcase causing the amount you see on the dipstick to read higher than if a quality filter with a silicone anti-drain back is used.

If you run the stock OEM size filters such as the Wix 51626 (metric) or the Wix 51085 (SAE) or the higher capacity Wix 51515 (SAE) or the gargantuan (fits VERTICAL only) Wix 51773 (SAE). As the Wix filters all have silicone anti-drain back valves you aren't as likely to get an erroneous high reading if you use a cheap filter.